I'm pretty sure that I followed the instructions perfectly. Some of my plants died unfortunately (pretty sure that I "overbleached"). I keep checking my nitrates/nitrites and they are fine, but now my water smells funny, and the fish are gasping at the top for air. I add a powerhead, and all is fine although the tank doesn't look appealing. So last night I take out the powerhead (which was in for several days) thinking that things are okay, and I wake up this morning to more gasping! Anyone have any suggestions?